(A) Field of the Invention
This invention concerns a fuel ignition apparatus which safely controls the passage of fuel to a fuel igniter.
(B) History of the Prior Art
In the prior art, apparatus for safely controlling the flow of fuel to an igniter were known; however, prior art apparatus had serious disadvantages. The first such apparatus were not electrically controlled but were devices subject to mechanical failure. The first such apparatus employing electric igniters were designed to permit the current to stop flowing through the igniter after commencement of combustion of the fuel. In such apparatus, means for stopping flow of current through the electrical igniter was necessary to prevent the igniter from rapidly burning out. In addition, complex systems were required to close the valve through which fuel was supplied in the event that fuel combustion accidentally ceased. Furthermore, such complex valve closing systems were not fail safe since if a critical component of the system became inoperative, a signal would not be supplied to close the fuel valve.
Improved electrical igniters were subsequently developed which permitted continuous flow of current through the igniter during the entire period that fuel flowed from the fuel source. The long life of the improved electrical igniter permitted the continuous operation of the igniter and systems were not used to turn off the igniter after combustion of fuel began due to the complexity of control apparatus and due to the failure of the prior art to provide a fail safe system which would assure that flow of fuel ceased even if a critical component of the system failed.
Examples of prior art patents which disclose igniters which are automatically deactivated after fuel ignition are shown in U.S. Pat. Nos. 1,694,053; 1,708,918; 1,774,137; 2,108,770; and 2,954,080. Each of these patents either discloses a highly complex electrical system which have bulky mechanical support mechanisms, or are not fail safe since the failure of only one particular critical component could permit the continuous flow of fuel without combustion.
For example, U.S. Pat. No. 1,694,053 discloses a complex electrical apparatus which is dependent upon the continued operation of two relays and if either of the relays were to fail in a closed position, fuel could continue to flow without ignition. U.S. Pat. No. 1,774,137 discloses a liquid fuel ignition apparatus which is complex and which is supported by a bulky bucket switch as its fail safe mechanism which would be entirely inoperative if the fuel were a gas. Similarly, U.S. Pat. No. 1,708,918 also depends upon a bulky bucket switch as a fail safe mechanism which would be inoperative if the fuel were a gas. U.S. Pat. No. 2,108,770 discloses a complicated electrical circuit which would permit the continuous flow of fuel without ignition if one set of electrical contacts (41 and 43) were to remain closed. The system is therefore not fail safe since failure of only one component will permit fuel to flow without ignition. U.S. Pat. No. 2,954,080 discloses a fuel ignition apparatus which is not fail safe since if the igniter fails, fuel can continue to flow without ignition and since if a critical relay failed, fuel could continue to flow without ignition.